The mass per unit volume of a substance; a less dense substance will float on top of a more dense one.

The term used for a gas or liquid because these can flow as their particles can move around.

Describes the movement of particles in a fluid that travels at a range of speeds in all directions.

The movement of fluids caused by differences in density within the fluid, which allows energy to be transferred as the hotter fluid rises to cooler areas.

Explaining convection

Combined science

In the Energy of moving particles unit, they will build on this knowledge to learn how the movement and nature of different particles transfers energy by conduction, and how specific heat capacity and specific latent heat quantify the effect of heating on the properties of a material.

In the Heating and cooling unit, pupils learnt how the motion of particles in solids, liquids and gases changes when they are heated, how thermal conduction and insulation work and why heating different materials doesn’t always increase their temperatures by the same amount. 

Particle explanations of density and pressure

The particles have a range of different speeds.

All particles move in the same direction.

Which of the following describe the motion of particles in a fluid?

The average speed of the particles is around 500 m/s.

The average speed of the particles is around 50 000 m/s.

If their average speed increases, the particles move farther apart.

If their average speed increases, the particles move closer together.

Which of the following statements about the particles in air are correct?

They collide with each other less frequently.

Which of the following describes what happens to particles of a fluid when the temperature of a fluid decreases?

Hotter fluid sinks because it is denser than cooler fluid.

Hotter fluid rises because it is denser than cooler fluid.

Hotter fluid sinks because it is less dense than cooler fluid.

Hotter fluid rises because it is less dense than cooler fluid.

Which of the following statements explains why convection can happen in a fluid?

This makes the air particles move faster and farther apart.

This makes the air expand, so some particles are pushed out of the balloon.

The air left inside the balloon is now less dense.

This makes the average density of the balloon decrease.

The balloon is now less dense than the surrounding air, so it rises upwards.

Sort the following statements into the correct order to explain how a hot air balloon can increase its height.

This makes the particles move faster and farther apart.

This makes the air expand, so its density decreases.

The air rises and spreads across the top of the room.

It then cools, contracts and becomes more dense.

A convection current occurs in a room after a radiator is switched on. Sort the following statements into the correct order to describe and explain how the convection current forms.

Gases and liquids can both flow. Because of this, they are both called {{}}.

The mass per unit volume of a substance, or object, is called its {{}}.

A {{}} is two or more atoms that are bonded together.

All of the particles are identical to each other.

The particles are vibrating around fixed points.

The particles are far apart compared to their size.

Which of the following statements describe the particles in any gas?

Which of the following describes what happens to the particles of a gas when the temperature of the gas rises?

It is less than the density of the surrounding air.

It is greater than the density of the surrounding air.

It is the same as the density of the surrounding air.

A hot air balloon in air is staying at constant height. Which of the following statements about the average density of the balloon (including the basket, the balloon and the air inside) is correct?

Starter Quiz